The bombing of a bus in Tel Aviv on Wednesday was less devastating than the suicide attacks that Israeli civilians endured in cafes, buses, beaches and restaurants during the second Palestinian uprising more than a decade ago.

But the explosion, which injured about 20 people, was still a reminder of how quickly the current Gaza conflict could escalate and spread deep into Israel.

The explosion came about nine hours before a ceasefire between Hamas and Israel went into effect. So far no one has claimed responsibility for the attack, which took place at noon on a nearly empty bus on a main road near the offices of the Israel Defense Forces.

The head of the political wing of Hamas, the Islamist group that rules Gaza, told CNN on Wednesday that his group was not responsible.

“Who created the circumstances which led to this operation?” asked Khaled Meshal. “It is (Israeli Prime Minister Benjamin) Netanyahu who with his crimes in killing the kids of Gaza and the continuity of aggression, he creates such ramifications everywhere.”

Israeli police spokesman Micky Rosenfeld told reporters at the scene that there was no warning of a specific attack and added, “it’s very clear that this is a terrorist attack.”

Israeli towns near Gaza regularly bear the brunt of rocket attacks but Wednesday’s bomb was the first of its kind in Tel Aviv since 2006, when a Palestinian man blew himself up next to a sandwich stand near a bus station.

During the second Palestinian intifada from 2000 to 2006, Hamas and other militant groups unleashed waves of suicide bombings and sniper attacks. Casualties on both sides were in the thousands as Israel retaliated.

For some long-time observers of the intractable Israeli-Palestinian conflict, the bus attack underlined the need to use Wednesday’s ceasefire following eight days of fighting as starting point for a political solution.

“Unfortunately, it shows the enemies of Israel that they can revert to their activities inside Israel,” said Professor Moshe Maoz, former adviser to assassinated prime minister Yitzhak Rabin. “Israel is not sealed, people can infiltrate.”

Speaking from Jerusalem, Maoz said the long-term solution to the conflict must be political, not military.

“It is a matter of psychology. People are fearful and they want revenge, but also Gaza people want revenge against Israel,” he said.

“Let’s say the ceasefire holds for a week or months but the fighting can renew, because Gaza is a very small strip of land and 1.5 million Palestinians are frustrated and hateful and they cannot go out.”

Moaz said Israel must improve relations with Turkey and Egypt, which could act as moderating influences on Hamas in the long term. Hamas is an offshoot of the Muslim Brotherhood, which governs Egypt. Egypt sponsored the ceasefire.

Turkey, another important broker in the conflict, has a moderate Islamist government in power.

The bus attack shows Israelis are not immune to Palestinian violence despite heightened security measures by the government over the years, said professor Mohamed Dajani at Al Quds University, speaking from Jerusalem.

“It is an indication that the security of the wall is a myth,” he said, referring to the controversial West Bank separation barrier that Israel says prevents suicide bombers from crossing into Israeli areas, but Palestinians say has isolated and imprisoned them.

“The Israelis have been saying there haven’t been suicide bombings in Tel Aviv and other places because of the wall but this bus attack shows it wasn’t the wall but it was Palestinian public opinion, which was against suicide bombing,” he said.

Dajani expressed concern there could be more attacks unless talks start on a lasting peace, because images of dead Palestinian children circulating on social media websites are whipping up anger. At least 160 Palestinians and five Israelis have been killed in the offensive.

“People’s emotions have been very much scared and as a result this escalation is only expected,” he said. “There is escalation of violence on both sides and it is civilians on both sides who are being hurt.”